JPH06252554A - Manufacture of multilayered printed wiring board - Google Patents

Abstract

PURPOSE:To enhance the position accuracy between printed wiring boards by attaching and bonding a bonding agent, whose glass transition temperature is specified, to a part of the conductor part of the roughened printed wiring board. CONSTITUTION:After conductors 4 of printed wiring boards 1a and 1b are roughened, a plurality of the printed wiring boards 1a and 1b are arranged through a bonding sheet 2a. Thereafter, the parts of the conductors 4 of a plurality of the printed wiring boards 1a and 1b are mutually bonded. As the bonding agent used for the bonding, the bonding agent, whose glass transition temperature is 120 deg.C or higher at least after the bonding, is used so as to reduce the position deviation in thermocompression bonding. It is preferable that the bonding agent is the thermosetting resin. It is especially preferable that the bonding strength per one bonding point is 10N or more at 150 deg.C. Thereafter, a bonding sheet 2b and a copper foil 5 are arranged at the outsides of a plurality of the printed wiring boards and held with end plates 6, and heating and compression are performed as required. Thus, the lamination and bonding are performed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a multilayer printed wiring board used in electronic computers, wireless equipment, electric power transmission equipment and the like.

[0002]

2. Description of the Related Art Generally, in a multilayer printed wiring board, a plurality of printed wiring boards on which a desired conductor circuit is formed are prepared in advance, and an adhesive sheet is interposed between the printed wiring boards, and if necessary, an adhesive sheet or Place copper foil or copper-clad laminate,
These are heat-pressed and laminated to form a laminate. It is particularly important in terms of quality of the multilayer printed wiring board to prevent the displacement between a plurality of printed wiring boards when performing the lamination bonding, and in order to prevent the displacement, a conventional method is disclosed in Japanese Patent Publication No. 55-22040. As described above, a method of punching a guide hole at a predetermined position of a printed wiring board, aligning the position with a guide pin, inserting the guide pin into a hole formed in a mold, and heating and pressing has been widely used. However, in the method described in Japanese Patent Publication No. 55-22040, it is necessary to use a jig or tool such as a mold or a guide pin having high positional accuracy, which requires a great deal of cost for producing the jig and the lamination. Since the adhesive sheet melted at the time of adhesion adheres the mold and the guide pin, there is a problem that workability is significantly deteriorated when the mold, the guide pin and the multilayer printed wiring board are disassembled after lamination. As a method for solving these problems and simply preventing the displacement, in recent years, as shown in JP-A-61-256696, a plurality of printed wiring boards are mutually fixed with an adhesive, The method of laminating and adhering is beginning to be adopted.

[0003]

Problems to be Solved by the Invention JP-A-61-2566
The method disclosed in Japanese Patent Publication No. 96 has a serious drawback in that the workability is improved, but the positional deviation after lamination and adhesion due to heating and pressing is large.

The present invention provides a method for manufacturing a multilayer printed wiring board which is simple and has a high positional accuracy of a plurality of printed wiring boards.

[0005]

A method for manufacturing a multilayer printed wiring board according to the present invention is a method for manufacturing a multilayer printed wiring board, in which a plurality of printed wiring boards are arranged via an adhesive sheet and thermocompression molding is applied to form a multilayer. In, the conductor portion of the printed wiring board is subjected to a roughening treatment in advance, and then a part of the roughened conductor portion is applied with an adhesive having a glass transition temperature (Tg) of 120 ° C. or more to bond the plurality of printed sheets. It is characterized in that the relative positions of the wiring boards are fixed and then the whole is thermocompression bonded. This will be described in detail with reference to the example of FIG. In a method for manufacturing a multilayer printed wiring board in which a plurality of printed wiring boards 1a and 1b are thermocompression bonded via an adhesive sheet 2a, a plurality of printed wiring boards 1a and 1b are previously prepared.
It is characterized in that the conductor portions 4a and 4b of b are bonded to each other with an adhesive 3 and then thermocompression bonded.

As shown in FIG. 1, the printed wiring board 1 has 1a,
Any number of 1b may be used as long as it is two or more. The printed wiring boards 1a and 1b may be so-called double-sided printed wiring boards having desired patterns of conductors 4a and 4b on the front and back surfaces illustrated in FIG. 1, but a multilayer printed wiring board having an arbitrary number of layers may be used. Further, in order to produce a high-density multilayer wiring board, it is desirable to use a so-called through-hole wiring board in which holes are made conductive at desired positions as the printed wiring board.

In the present invention, it is necessary to roughen all or part of the conductors 4a and 4b of the printed wiring boards 1a and 1b prior to bonding. Roughening treatment includes mechanical roughening with abrasive grains, chemical treatment such as soft etching and oxidation treatment,
Although any method can be used, it is preferable to treat with an oxidizing chemical treatment liquid represented by an alkaline sodium sulfite solution or the like, since the roughened shape is dense and the adhesive strength of the adhesive thereafter can be secured. These printed wiring boards 1
a and 1b are arranged via the adhesive sheet 2a. The adhesive sheet 2a can be made of any material as long as it can be molded by heating and pressurization, but generally a so-called prepreg made of resin and glass cloth cured in a beater stage can be used. Any number of adhesive sheets can be used here. This adhesive sheet 2 should not be present in the adhesive portion because it is bonded by the adhesive. As a method of removing the adhesive sheet at the adhesive-bonded portion, as illustrated in FIG. 1, a method of notching the corresponding portion of the adhesive sheet, a method of using an adhesive sheet having a smaller size than the printed wiring board, or the like can be used. After that, the conductor portions of the plurality of printed wiring boards 1a and 1b are bonded to each other with the adhesive 3. The adhesive used for joining can be any adhesive such as epoxy resin, phenol resin, phenoxy resin, silicone resin, polyimide resin, polyamide resin, urea resin, melamine resin, allyl resin, furan resin, polyester resin, polyurethane resin, etc. However, in order to reduce the positional displacement during the subsequent thermocompression bonding, it is necessary to use a glass transition temperature (Tg) of at least 120 ° C. or higher after bonding.

Since this adhesive must withstand the temperature during the subsequent thermocompression bonding and prevent the positional displacement between the wiring boards,
A thermosetting resin is preferable, and a joining strength per joining point is particularly preferably 10 N or more at 150 ° C.

As a method of adhering with an adhesive, an arbitrary method can be used, as shown in FIG. 2, in which an adhesive previously sandwiched between printed wiring boards is brought into contact with a heated iron and adhered by heat. Can be used. However, in consideration of workability and thermal damage to the printed wiring board, a method of applying ultrasonic vibration to an adhesive previously applied between a plurality of printed wiring boards as shown in FIG.

The printed wiring board may be adhered to any desired location, but it is preferable that the number of adhering locations be at least 8 points included on the four sides of the printed wiring board in order to reduce the amount of displacement from the adhering location.

Thereafter, if necessary, an adhesive sheet 2b and a copper foil 5 are arranged on the outer sides of a plurality of printed wiring boards, sandwiched between end plates 6, and heated and pressed to laminate and bond them. heating·
The pressurizing means and conditions can be the same as conventional ones.

[0012]

According to the conventional method disclosed in Japanese Patent Laid-Open No. 61-256696, a multilayer wiring board can be efficiently manufactured by a simple method without using a special mold, but printing after thermocompression bonding is often performed. There is a problem that the amount of misalignment between wiring boards is large. As a result of a detailed examination of the cause of this, Japanese Patent Laid-Open No. 61-25
The bonding with epoxy resin, phenol resin, polyimide resin, silicone resin, polyurethane resin, polyamide resin, nitrile rubber, chloroprene rubber, butyral resin, cyanuacrylate resin, double-sided tape, which are specifically exemplified in 6696, It was found that, in all cases, the amount of displacement increased due to the decrease in the bonding strength at the temperature (generally 150 ° C. or higher) during the subsequent thermocompression bonding. In the present invention, the adhesive is applied to the conductor portions of a plurality of printed wiring boards by applying an adhesive, the conductor surface to be adhered is roughened beforehand, and the adhesive has a glass transition temperature of 120 ° C. or higher. By using a product, it is possible to reduce the deviation amount while maintaining the convenience of manufacturing.

[0013]

[Example] As a result of various studies on the adhesive and the bonding method used for bonding, it was found that the tensile strength under heating of the bonding point is important in order to reduce the amount of displacement between the printed wiring boards. Specifically, a test was conducted in which the bonded wiring board was heated to a predetermined temperature in air and a force of 10 N was applied to each bonding point. It was found that the amount can be significantly reduced. Table 1 shows the heat resistance of cyanu acrylate resin bonding, which is exemplified as the most preferable method in JP-A-61-256696, and the heat resistance of the adhesive and the bonding method of the present invention in comparison.

[0014]

[Table 1] Heat-resistant temperature is 1 cm ^{2 of two} printed wiring boards The temperature at which the parts are adhered by a predetermined method and heated and peeled while applying a stress of 10 N is described.

Although any method can be used for the adhesion of the present invention, the ultrasonic adhesion method can selectively apply ultrasonic energy to the adhesive portion, and the other portion of the printed wiring board. Since it is difficult to cause heat damage or dimensional change due to heat, it is possible to manufacture a multilayer printed wiring board with a particularly small amount of positional deviation.

As a bonding method with high heat resistance, brazing with solder or the like can be considered in addition to the present invention. However, when brazing is performed, the conductor surface to be brazed must be clean. There are difficult drawbacks. Further, in brazing, it is necessary to heat the brazing filler metal to a temperature higher than the melting point of the brazing filler metal, and when the printed wiring board is thick or when three or more printed wiring boards are adhered to each other, thermal damage or heat may occur at the joint portion. There is a drawback that it is easy to give dimensional changes. According to the method of the present invention, since an adhesive is used, position fixing having heat resistance equal to or higher than that of brazing can be realized without using excessive heating means. In addition, when the relationship between the bonding location and the positional shift amount was examined, there was a correlation between the number of bonded sides and the shift amount, and it was found that the four sides, eight points, and four sides from the four sides and four points of two sides shown in FIG. It was found that the deviation amount was small at 12 points. Comparing the method of the present invention and the method of thermocompression bonding using the guide pin, the method of using the guide pin is a method of preventing the positional displacement only with the hole cross section of the relatively thin printed wiring board, and the hole is deformed. On the other hand, since the method of the present invention is a method of preventing the positional deviation on the surface of the conductor pattern having a predetermined area, the positional deviation is less likely to occur.

Example 1 An example will be described with reference to FIG. A printed wiring board 2 having a desired conductor pattern by etching resist patterning and etching a glass cloth epoxy resin copper-clad laminate MCL-E-67 (trade name, manufactured by Hitachi Chemical Co., Ltd.) having a thickness of 0.4 mm by an existing method. Sheets 1a and 1b were obtained. afterwards,
0.2 as an adhesive sheet 2a between the printed wiring boards 1a and 1b
mm glass cloth epoxy resin prepreg GE-67N
(Hitachi Chemical Co., Ltd., trade name) is sandwiched between the printed wiring boards 1a and 1b, and the adhesive 3 is 0.1 mm in the four corners.
Heat-resistant epoxy resin adhesive sheet Anisolmu (trade name, manufactured by Hitachi Chemical Co., Ltd.) was placed. Then, as shown in FIG. 2, the four corners were heated and bonded at a temperature of 270 ° C. for 30 seconds using a commercially available soldering iron to bond them. After that, as shown in FIG. 1, 0.2 mm glass cloth epoxy resin prepreg GE-67N (trade name, manufactured by Hitachi Chemical Co., Ltd.) was used as an adhesive sheet 2b on the outside of the wiring board, respectively, and copper having a thickness of 18 microns was used. The foil 5 is placed, sandwiched between the end plates 6, and the molding temperature is 170 ° C. and the molding pressure is 40 kg / cm ^2. 90 minutes by thermocompression bonding, plate thickness 1.5m
A 6-layer multilayer printed wiring board of m was obtained.

Example 2 A 6-layer multilayer printed wiring board was obtained in the same manner as in Example 1 except that the adhesive of Example 1 was replaced with a semi-cured polyimide sheet having a thickness of 0.05 mm.

Example 3 In the bonding method of Example 1, as shown in FIG. 3, an ultrasonic vibrator was brought into contact, and an ultrasonic wave with an output of 1 KW and a frequency of 28 kHz was applied to 1.
A 6-layer multilayer printed wiring board was obtained in the same manner as in Example 1 except for the method of bonding by sending for 0 seconds.

Example 4 The bonding points of Example 3 were changed from four corners of the printed wiring boards 1a and 1b to eight points including four sides of the printed wiring board shown in the plan view of FIG. A 6-layer multi-layer printed wiring board was obtained by the same method as described above.

Table 2 shows the working time and the amount of positional deviation in the above-described first, second, third, and fourth embodiments in comparison with the conventional method.

[0022]

[Table 2]] The working time was measured as the time required for bonding with an adhesive.

[0023]

As described above, when the method of the present invention is used, the result that the displacement amount is small is obtained. Regarding Examples 3 and 4, although a predetermined device was required for brazing, the working time was particularly short, and the best result was obtained in which the amount of positional deviation was extremely small.

[Brief description of drawings]

FIG. 1 is a plan view and a cross-sectional view of a multilayer printed wiring board before thermocompression bonding showing an embodiment of the present invention.

FIG. 2 is a schematic view showing an example of a bonding method according to an embodiment of the present invention.

FIG. 3 is a schematic view showing an example of a bonding method according to another embodiment of the present invention.

FIG. 4 is a schematic view showing an example of a bonding portion of another embodiment of the present invention.

[Explanation of symbols]

 1. Printed wiring board 2. Adhesive sheet 3. Adhesive 4. Conductor circuit 5. Copper foil 6. End plate 7. Soldering iron 8. Ultrasonic transmitter 9. Ultrasonic power supply

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Claims (4)

[Claims] 1. In a method for producing a multilayer printed wiring board, wherein a plurality of printed wiring boards are arranged via an adhesive sheet, and thermocompression molding is applied to make a multilayer, a conductor portion of the printed wiring board is roughened in advance, and then the printed wiring board is roughened. An adhesive having a glass transition temperature (Tg) of 120 ° C. or higher is applied to and adhered to a part of the roughened conductor portion to fix the relative positions of a plurality of printed wiring boards, and then thermocompression bonding the whole. A method for manufacturing a multilayer printed wiring board, comprising: 2. The method for producing a multilayer printed wiring board according to claim 1, wherein the adhesive is a thermosetting resin, and the bonding strength per bonding point is 10 N or more at 150 ° C. 3. The multi-layer printed wiring according to claim 1, wherein the bonding method is a method of bonding by applying ultrasonic vibration to an adhesive previously applied between a plurality of printed wiring boards. Method of manufacturing a plate. 4. The bonding points are 8 points or more including at least 4 sides of the printed wiring board.
4. The method for manufacturing a multilayer printed wiring board according to any one of 3 above.